Solenoid actuator



July 25, 1967 G. L( ARBUTHNOT HI SOLENOID ACTUATOR Filed Jan. 25, 1964 2 Sheets-Shee 1 INVENTOR. GUY L. ARBUTI-/NOTM FG I A TTORNEY United States Patert O ice SOLENOID ACTUATOR Guy L. Arbuthnot III, Patrick AFB, Fla., assignor to the a United States of America as repre'sented by the Secretary of the Navy i Filed Jan. 23, 1964, Ser. No.'339,`831

4 Claims. (Cl. 317-155.5)

' The invention described herein may be manufactured and 'used -by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates generally to solenoids and v in particular is a non-ferrous solenoid actuator which operates within a negligible self-generated ambient electrornagnetic field for most practical purposes.

v In the past, solenoids consisted of an electrically enerpurposes, such -arrangement also createsa considerable,

external magnetic field which -adversely affects or' limits its use. For example, in magnetometer Operations, mine hunting Operations, or any other operation where the presence of spurious magnet ic fields may interfere with the object or things being determined or hunted, it;is.

definitely undesirable to have magnet ic fields emanating from the equipment used in the determining .or hunting process. Such interference may not only be distracting and error producing, it may defeat the operation entirely. In the case of the hunting of mines of unknownresponse characteristics, such magnetic fields may also present a safety hazard to the personnel involved because 'they may cause said mines to be prematurely or inadvertently exploded, in event they are' of the magnetic type.

The instant invention overcomes most of the disadvantages of the prior art solenoids 'using ferrous material plungers, in that only a neglig ible magnetic field of the order of .0*3 10- gauss is produced thereby at a five foot radius therefrorn.

lt is, therefore, an object of this invention to provide an` improved electromagnetic actuator. i

Another object of this invention -is to provide an improved solenoid type actuator having only a. negligible ambient magnetic field.

Still another object of this invention is to provide a solenoid actuator that does' not magnetically interfere with or adversely affect apparatus associated or contiguously disposed therewith. a i

Another object of this invention is to provide a nonferrous electromagnetic solenoid type of mechanism actuator.

Another object of this invention is to provide an improved solenoid actuator for a snap valve.

Another object of this invention is to provide a nonferrous plunger control mechanism for a controllable valve. i

Still another object of this invention is 'to provide an improved method and means of providing motor force to a mechanism in the presence of magnetometers, magnetic mines, and other magnetic or electromagnetic equipment which will not intefere therewith or cause same to become a safety hazard.

3,333,162 Patented July 25, 1967 Another object of this invention is to provide an improved method and means for producing a mechanical force from electrical power.

Another object of this invention is to provide an im-` proved, non-ferrous, non-interfering actuator for relay switches or the like.

Another object of this invention is to provide an improved electromagnetic solenoid type actuator that is easily and economically manufactured, maintained, and operated.

` Other objects and 'many of the' attendant advantages will be readily appreciated as the subject invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings and wherein:

FIG. '1 is ?a diagrammatical representation with parts broken away of the solenoid constituting this invention;

-FIG, 2 is a graphical representation of the theory of a single loop of wire which provides the`basis f-or'a mathematical definition of the invention;

FIG. 3 `depicts the geometry for calculation of the internal field of a solenoid of the type incorporated in 'this 'i invention;

FIG. 4 isa graphical representation of field streugth (H) values along four selected radial lines;

FIG. 5 is a block diagram illustrating the subject invention being operationally connected to any appropriate utilization apparatus; and

FIG. 6 is a schematic representation of the electrical interconnect'ions of the coils incorporated in this inventionr ?Referringnow to FIG( 1, the subject solenoid 10 is` shown as having a first inner'coil l lxthat rotates about a' fixed' axis X when activated by a current in the field of a second coil -12 which surrounds coil 11 and is wound in a direction norr nal thereto. A third coil 13 part-ially sur rounds coil 12 and completely surrounds coil 11, and a fourth coil 14 completely surrounds coils 11 and 12 and partiaI-ly surrounds coil 13. Coils '13 and 14`a're wound in opposite directions to coils '11 and' 12, respectively, in

V order to insure the minimum possible external magnetic disturbance. Furthermore, coils 11, '12, 13 and 14 are connected in series, preferably in that order.

` Coils 11 through'14 are each respectively wound on round forms or spools 15 through 18 with the material thereof be-ing'non ferrous and, theref-ore, not responsive toor reactive with magnetism or electromagnetic fields of any kind. Examples of suitable materials for such forms areplastic, Wood, paper, aluminum, magnesiurn, or the' like, that have the appropriate shape and'strength characteristics. Of course, each of coils 12 through 14 are held in place with respect to each other by any conventional supporting materials such as cement, potting material, or the like, likewise not containing any ferrous or other magnetically responsive material. Furthermore, the entire invention may be incased within any suitable non-ferrous nonmagnet-ic housing 26 or any metallic or nonmetallic shielding which may, for instance, insulate it electrically, electromagretcally, and' physically from its ambient environment.

Because coil 11- is intended to rotate about axis X, it may be conventionally mounted on an appropriate shaft 19, which, in turn, mayrotate in' suitable bearings 20 10- cated within and mounted on frame 17 of coil 12 by any appropriate conventional mount-ing means 21. So doing would be obvious to one skilled in the 'art having the benefit of the teachings heroin presented. Likewise, other suitable arrangements which perform as desired would also be obvious tot-he artisan. consequently, these conventional and well known structural features are not considered to be necessary :to disclose the inventive aspect of this invention and are, therefore, omitted from FIG. 1 to prevent its being cluttered with unnecessary details.

The design of coils 11 through 14 is of some importance in this particular case. The following exemplary table of preferable parameters are thus presented:

Coil No. No. of Turne No. of Layers Wire Size B: 1.25 H=3.00 C=1.00 1:5.34

D: 1.75 J=approx. 5.0 E=approx. 0.25 K: approx. 6.25 F=2;30

It should, therefore, be understood that all of the foregong preferable parameters are merely exemplary and that other operable desigus may be employed if operationa l circumstances so warrant. Hence, the invention discl-osed herein' should not be considered as being limited to the above preferable design parameters.

A plunger 22, which preferably has a one ounce weight, is connected to a bear-ing 23 which, inturn, `is integrally or otherwise attached to form 15 of col 11. Apertures 24 and 25 respectvely are located in frames 17 and 18, in order to allow plunger 19 to moveably extend therethrough. The aforesaid housing 26 may likewise contain a similar aperture to allow plunger 22 to extend therethrough. Of course, plunger 22 is also made of any suitable non-ferrous materialhav ing the desired strength characteristics for proper operation and is adapte-d for connection to and actuation of any pertinent associated apparatus.

To facilitate Understanding the actual operation of the subject invention, which is to be discussed subsequently, the theory for calculating the respective parameters of a minimum external magnetc field solenoid is now presented. The symbols used in this theoretical and mathematical presentation are as follows:

A-Vector potential B-Magnetic inducton A- Vector operator ,u-Permeability I--Current F-Force r- Forque a--Radi us of solenoid l- Length of solenoid N-Number of turns of solenoid ---10- gauss (in air) =--Equal -Greater than -Much greater than Less than E--Defined as --Vector characterstic 4 -Angle 0-Angle P-Point r- Distance X-Axis distance Y-Axis distance Z-Axs distance The purpose of the system illustrated .in FIG. 1 is to raise plunger 22, having a weight of one ounce of less, a very small distance with a minium magnetic disturbance external to the system. As previously mentioned, Coil No. 11 rotates about a fixed aXis x when activated by a current in the field of Coil No. 12. Coil Nos. 13` and 14 are wound in opposite directions to No. 11 and No. 12 respectvely to insure the minimum possible external dist-urbance. It is desired that the combined B's of the four solenoids be less than 0.03 (3 10-' gauss in air) five feet from the system. Two minor assumptons were made but thenumber of turns in solenoid No. 13` and No. 14

may be adjusted for the desired effect in actual construc tion. The following theoretical calculations are based on a steady current flow; however, the results may be applied to reasonably low frequency alternating current, certainly within Construction lim-itations.

The theory of a solenoid is based on the theory of a single lo-op of wire which is where this calculation begins.

Using FIGURE 2 and a basic electromagnetic fact, name-` ly that the magnetic induction B is given by B=A A where A, the vector potential is defined by 13 L i ro (2 It should be noted that dA and ds are in the same direction, and from FIGURE No. 2 a comp onent of A cancels one Component of A leaving from all the dilferential elements only the cos qi component for the total A. Equation 2 is now rewritten as It has been shown in FIGURE No. 2 by the Law of Cosines that q +p2- p l also o zz rq thus o=\ +p p cos d' Substitution of (4) into (3) yields a cos bdqs At a distance much greater than the radius of the coil, a may be neglected in comparison to Z or r EZ +p a (6) and (5) becomes I W a cos d A m 2, 0 VZ -I-p --2ap cos 4 7 By using the first par-t of 6) E a cos qsd s 1% r -2a cos 4 (8) V 1 ap i l (7 2ap cos q) 12 T+ 3 COS qS-l- Thus using (9) in (8) .and performing the indicated integration AW sin 6 Where P sin 0- T The problem of choosing a convenient coordnate system now presents itself. In the preceding discussion, it is noted that spherical coordinates seem to be convenient. The coil, having a cylindrical shape, might lead one to cylindrical coordinates, however, in this case, the results rvolve complete elliptic integrals of the first and second kind. Cylindrieal coordinates present the results in such a complicated form, the functional relation of physical par'ameters are obscure. Since the problem Will presently involve four hypothetical solenoids, listed as No. 1, No. 2, No. 3, and No; 4, each presenting three parameters and two field Components, thesimplest original expression is most desirable.

The curl of any Vector in spherical coordinates is given by i Since only the Component is present Thus, where r a i( outside of the loop),

and for a solenoid of N turns and r a a NI ;ia NI Of ir (15 For future'referenc'the field' inside a solenoid is given by FIGURE 3 and the following and at the ends na 21 (21) The above neglects the "shielding effect of outer solenoids on inner solenoid, which is functionally proportional to the current; The system involves 2 pairs of solenoids perpendicular to each other. For reasons presented later, in the discusison of the torque on solenoid No. 1, it is possible to treat the pairs of solenoids separately, remembering that one may practically null the field of No; 1 by No. 3 at some distance, resulting only in a net field of B -B to rotate coil No. 1, hence the lifting plunger.

consider 2 concentric solenoids I and II by way of illustraton:

OUTSIDE E H- II I1 rr OOS 9 outside uI1N a COS 0 E HI II 11 11 S 6 1 11 4,3 outside outside i and if the solenoids are connectedin series a B is given by Substituting (22 and (23 into (24) outside e i outside Adding under the radical outside outside (26 Max. outside Thus, if it is possible to hold the maximum outside to 0.03'y at 5 feet, the purpose of the calculation has been accomplished.

The following deals entirely with the application of the precedng results, the use of certain assumed practical parameters and calculation of others. The field of solenoid No. 1, itself, has no use; hence, we -wish to completely null it with No. 3, thus at r a a (28) is give'n by outside Inside the solenoids No. 1 and No. 3, from (20) l ]inaide l la I (3 If (31) is to be approximately zero also,

this means that La N -l (32) Combining (32) and (30) r & h

3 3 l The next requi'ement is for outside at its maximum possible value at 5 feet. One cannot a bitrarily set E max= at this distance as was done a for No. 1 and No. 3 since (B inside solenoid #2) must be above a certain minimum to insure rotation of solenoid No. 1. For an approximate answer B (outside) is set -to equal 0.037 at feet and it turns out that experimentally the field tends to zero past this point.

The following conversion factors to mks system are now used: v

' 1 gauss=- webers/meter 5 fLzLS meters Henrys z z "7 ;1.0 p. air uplastc 41rX10 meter [This is good to 1 part in 100,000,000]

1 inch=2.54 10- meters.

'8 Then,

(10 4 5 0.03 10' gauss W (2)(1.5 meter) 2.54x 10- 47rI 1o- Henry meter lNz z i i l (35) Thus,

N2a22 N4a42 I( 12.57) 6.45) o- Note: a and a have units of inches and 0.25 1 N2a22"N4a42`T H (36) The above is outside the system. Inside the system the torque that B inside must exert on solenoid No. 1 must be (1 oz) a oZ-inches. Since the torque is given by T=dF r=dF a sin #=(N1I)B (a 7r) (37 inside Rewritter T =7ra (N I)B (38 inside The field inside No. 2 acting on solenoid No. 1 is given by Ng N4 7; E] (39) inside #2 Combning (38) and (39) #`=7r (NI) l 1 40 N N 2 z zl] M kilogram -2 T (9.8 )(1 oz. ((2.83 1o WWW, L

lg l4 & &] (9.s)2.s3 10 -7rt1I ;LN 2 h (41) 2.83 1o- 2 (3.14) 12.57 10- NI 12 14 3 2 [E (9.8) 7.0 7 10 -a IN lz 24 (42) 69.2 10 =a,I N lir-@ lg li At this point, it is very useful to collect all known relationships. i &gaggy N a a 36 1 2 2= (43) and (42) a I N =69.2 10- 2 14 v where a and 1 are given in inches, I in amps, and N in turns.

By starting with the desired current and dimensions of the solenoid, it is possible with the equations in (43) to calculate the number of turns needed in each coil. The numerical calculation for the solenods described herein as coils 11 through 14 are shown in the foregoing table of parameters. It is important to note, however, that (42) is valid only for a one ounce weight thus in general case (42) is written The size of the solenoid shown in FIGURE l can be decreased; the exhibited dimensions represent sizes that were easy to work with to establish feasibility. The calculated values and the experimental values were very close, which establshed that neglecting the sizeof the coils for field calculations Was practical, as may be discerned by inspection of FIGURE 4.

Briefly, the actual operation of the subject invention will now be discussed in connection with FIGS. 1, 5, and 6.

As shown in FIG. 5, a power supply 31 (which may be either a direct current or alternatng current power supply, depending on the selection of parameters mentioned above and the frequency involved), has its output coupled through a switch 32 to the input of solenoid to timely supply electrical energy thereto.

This electrical energy, in turn energizes each of the series connected coils 11 through 14, depicted schematically in FIG. 6, which, then, act as a plurality of interacting inductances. The magnetic fields generated by coils 11 and 12 react in such manner as to apply a torque to coil 11 and its associated rotatable form 15, thereby causing it to turn on axis X an amount suicient to move plunger 15. For the fore-going theoretically proven reasons this occurs, even though no ferrous material cores or plungers are employed. Plunger 22, of course, as a result of its connecting rod action, actuates any appropriate utilization apparatus 33 by applying a substantially unidirectional force thereto.

Because coils 13 and 14 are wound in opposite directions to 11 and 12, respectively, their magnetic fields inter-act to eifectively cancel the magnetic fields, if any, that escape the Physical periphery of coil 12. In this way, the total spurious. external magnetic disturbance is held to a minimum; in this case, 3 10- gauss in air, five feet from the system. For most practical purposes, including being used in magnetic mine hunting Vehicles and mine oountermeasure devices, this amount of ambient magnetism is negligible and presents practically no danger and no adverse operational effects. Accor-dingly, for such purposes, it is considerably Safer and better than most of the prior art solenoid type electromagnetic actuators in i operation at the present time.

Obviously, many modifications and other embodiments of the subject invention will readily come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing description and drawing. Therefore, it is to be understood that this invention is not to be limited thereto and that said modifications and embodiments are intended to be included within the scope of the appended claims.

What is claimed is:

1. Means for producing a force along a predetermined path comprsing in combination:

rotatable means for producing a first electromagnetic means spatially disposed around said first electromagnetic field producing means for producing a second electromagnetic field capable of interacting with said first electromagnetic field in such manner as to effect rotation of said rotatable first electromagnetic field producing means;

means spatially disposed around said first and second electromagnetic field producing means for producing a third electromagnetic field that is in opposition With said first electromagnetic field an amount suflicent for the eifective cancellation thereof only at a predetermined radial distance external to and substantially surrounding the outer periphery of said second electromagnetic field;

means spatially disposed around said first, second, and

third electromagnetic field producing means for producing a fourth electromagnetic field that is in opposition with said second electromagnetic field an amount sufficient for the effective cancellation thereof only at a predetermined radial distance external to and substantially surrounding the outer periphery of said third electromagnetic field;

means hn-ged to said first electromagnetic field producing means for converting the rotary movement thereof to proportional motion and force along a predetermined path; and

means effectively connected to each of the aforesaid electromagnetic field producing means for the disposition thereof in a predetermined operable geometrical c`onfiguration.

2. The invention according to -clairn 1 further characterized by a non-magnetic housing incasin g said electromagnetic field producing means in such manner as to eifect electromagnetic and physical insulation thereof from their ambient operational environment.

3. A solenoid comprising in combination:

a first electrically inductive means;

a second electrically inductive means surrounding said first electrically inductive means;

a third electrically inductive means surounding said -first and second electrically inductive means and having a polarity that is opposite the polarity of said first electrically inductive means;

a fourth electrically inductive means surrounding said first, second, and third electrically inductive means and having a polarity that is opposite the polarity of said second electrically inductive means;

means interconnecting said first, second, third, and fourth electrically inductive means for electrically connecting same in series;

means effectively connected to said first and second electrically inductive means for providing relative rotation oapability therebet'ween; and

means efiectively connected to all of the aforesad electrically inductive means for maintaining each thereof in operational dispositions relative to the others to effect substantially magnetic field neutralization at a predetermined distance from the outer periphery thereof, while enabling relative rotation to occur between the aforesaid first and secon-d electrically inductive means when a predetermined electrical energy is supplied thereto.

4. The invention of claim 3 further characterized by means connected to said first electrically inductive means for converting the rotation thereof into a force proportional thereto along a predetermined linea' path.

References Cited Karapetoff:` Experimental Electrical Engineering, Electro-Dynamometer Instruments, pages 42, 43, 44, 45, published in 1908, by John Wiley 'and Sons.

MILTON O. HIRSHFIELD, Primary Exam'ner.

MAX L. LEVY, LEE T. HIX, Exam'ners. 

1. MEANS FOR PRODUCING A FORCE ALONG A PREDETERMINED PATH COMPRISING IN COMBINATION: ROTATABLE MEANS FOR PRODUCING A FIRST ELECTROMAGNETIC FIELD; MEANS SPATIALLY DISPOSED AROUND SAID FIRST ELECTROMAGNETIC FIELD PRODUCING MEANS FOR PRODUCING A SECOND ELECTROMAGNETIC FIELD CAPABLE OF INTERACTING WITH SAID FIRST ELECTROMAGNETIC FIELD IN SUCH MANNAR AS TO EFFECT ROTATION OF SAID ROTATABLE FIRST ELECTROMAGNETIC FIELD PRODUCING MEANS: MEANS SPATIALLY DISPOSED AROUND SAID FIRST AND SECOND ELECTROMAGNETIC FIELD PRODUCING MEANS FOR PRODUCING A THIRD ELECTROMAGNETIC FIELD THAT IS IN OPPOSITION WITH SAID FIRST ELECTROMAGNETIC FIELD AN AMOUNT SUFFICIENT FOR THE EFFECTIVE CANCELLATION THEREOF ONLY AT A PREDETERMINED RADIAL DISTANCE EXTERNAL TO AND SUBSTANTIALLY SURROUNDING THE OUTER PERIPHERY OF SAID SECOND ELECTROMAGNETIC FIELD; MEANS SPATIALLY DISPOSED AROUND SAID FIRST, SECOND, AND THIRD ELECTROMAGNETIC FIELD PRODUCING MEANS FOR PORDUCING A FOURTH ELECTROMAGNETIC FIELD THAT IS IN OPPOSITION WITH SAID SECOND ELECTROMAGNETIC FIELD AN AMOUNT SUFFICIENT FOR THE EFFECTIVE CANCELLATION THEREOF ONLY AT A PREDETERMINED RADIAL DISTANCE EXTERNAL TO AND SUBSTANTIALLY SURROUNDING THE OUTER PERIPHERY OF SAID THIRD ELECTROMAGNETIC FIELD; MEANS HINGED TO SAID FIRST ELECTROMAGNETIC FIELD PRODUCING MEANS FOR CONVERTING THE ROTARY MOVEMENT THEREOF TO PROPORTIONAL MOTION AND FORCE ALONG A PREDETERMINED PATH; AND MEANS EFFECTIVELY CONNECTED TO EACH OF THE AFORESAID ELECTROMAGNETIC FIELD PRODUCING MEANS FOR THE DISPOSITION THEREOF IN A PREDETERMINED OPERABLE GEOMETRICAL CONFIGURATION. 